Arrangement on sewing machines for severing the thread chain

ABSTRACT

THE ARRANGEMENT FOR CUTTING THE THREAD CHAIN BETWEEN TWO WORK BLANKS ON A SEWING MACHINE COMPRISES AN UP AND DOWNWARD MOVABLE CUTTER ARRANGED BEHIND THE NEEDLE PARALLEL TO THE PRESSER BAR AND A STATIONARY COUNTERCUTTER ARRANGED IN THE PROXIMITY OF THE STITCH FORMING LOCATION WHERE THE PRESSER FOOT BAR IS CIRCULAR IN CROSS SECTION AND THE OPERATING BAR FOR THE MOVABLE CUTTER IS ARRANGED COAXIALLY THEREWITH.

United States Patent Inventor Appl. No.

Filed Patented Assignee Priority ARRANGEMENT ON SEWING MACHINES FOR Gerhard Mnrdter [56] References Cited s Gem"! UNITED STATES PATENTS 95 2,605,729 8/1952 Enos J 2,293,236 8/1942 Anderson a AG 3,250,237 5/1966 Myska Kaiserslautem' Hall German, 3,330,236 7/1967 Des Ormeaux et al Dec. 19, i968 Primary Examiner-James R. Boler Germany Attorney-Robert H. Jacob l l2/252 ll2/252 112/252 ll2/252 ABSTRACT: The arrangement for cutting the thread chain SEVERING THE THREAD CHAIN between two work blanks on a sewing machine comprises an I 2 Drawing Figs up and downward movable cutter arranged behind the needle [1.8. CI 112/252 parallel to the presser bar and a stationary countercutter arlnt.Cl D05b 65/00 ranged in the proximity of the stitch forming location where Field of Search .f. 1 12/252, the presser foot bar is circular in cross section and the operatl29, l-30 ing bar for the movable cutter is arranged coaxially therewith.

BACKGROUND OF THE INVENTION The invention relates to thread cutters for sewing machines. More in particular the invention relates to an arrangement for cutting the thread chain between two work blanks that follow one another.

It is already known to provide a cutting device for severing the thread chain on successive work blanks behind the stitch forming location of a sewing machine that consists essentially of a movable cutter and a stationary counter cutter arranged in the stitch plate. The movable cutter is connected with an operating bar which is moved by an electromagnet that acts against the force of a return spring and thus moves the cutter up and down behind the stitch forming location.

In arrangementsof this type a light gate serves for controlling the electromagnet, whose reflector which is freed by the emerging work blank, briefly closed the circuit of the magnet by way of a suitable amplifier.

Due to the wide space between the stitch forming location and the cutter, devices of this type involve the shortcoming that the ends of the thread chains that remain on the work blank are relatively long. Recognizing these shortcomings attempts have been made to move the movable cutter along an obliquely extending path to thus bring the edge thereof as closely as possible to the stitch forming location s the sewing machine. These solutions, however, involve relatively heavy structural expenses because they require guiding means for the operatingbar of the cutter that extend obliquely with respect to the material presser bar or to the needle bar externally of the machine housing, and they are unsuitable especially for machines operating with several needles referred to as overlapping sewing machines with thread preplacers. Owing to the fact that the thread preplacers require drive means disposed on the presser foot, the access to the stitch forming location is rendered difficult.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide an arrangement for cutting the thread chain, which is of simple construction while it provides the possibility to operate with several needles even with overlap sewing machines to sever the thread chain in the area of the stitch forming location, i.e., closely to the work blank.

In accordance with the invention this is accomplished in that the presser foot bar is of circular cross section and the bar that actuates the cutter is arranged coaxially with respect to the presser foot bar. In this manner it is accomplished that the presser foot barcan be used simultaneously as a guide socket for the bar .for moving the cutterwhich moves parallel to it and thus the cutter can be arranged closely behind the end of the sole of the presser foot, i.e., below the fastening eyelet thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described hereinafter with reference to an embodiment illustrated in the accompanying drawings in which:

FIG. I is a perspective illustration of the cutting device on a partially illustrated sewing machine, and

FIG. 2 is a section through the head of the sewing machine.

DESCRIPTION OF THE INVENTION The sewing machine arm 1 is, for example, the arm of an overlap sewing machine that operates downwardly along the arm, equipped with several. needles and which in a known manner has a head 2, a support or base that is not illustrated, and a material carrier arm 3. The needle bar 4 is mounted in the head 2 and supports needles 5 that cooperate at their lower ends with loopers which are not illustrated. The thread fingers that carry the overlap threads as is conventional with this type of machine arenot shown to simplify the illustration.

A presser foot bar 6 ts ournaled in the head of the sewing machine which is of circular cross section and is provided at its lower end with a presser foot 8 that presses the material being sewn upon the material feed dog 7 arranged in the material carrier arm 3. The presser foot 8 is provided in a manner likewise known per seat its bottom with a sole 9 formed out of sheet metal which keeps the presser foot in yielding engagement with the material being sewn.

The presser foot bar which is in the form of a hollow body carries an adjusting ring 10 in the area of its upper end which serves as a counter bearing for the spring II, the free end of which is biased against a pressure member 12 threadedly received in the head of the sewing machine.

Coaxially with respect to the pressure bar 6 and within the same a cutter rod 13 isarranged which serves for actuating the cutter, the upper end of which rod is connected with the armature of an electromagnet 15 which is secured to the head of the sewing machine by means of a socket 14. The electromagnet operates against a spring 16 that returns the rod 13 to its starting position, one end of which is supported against the pressure member 12 and whose other end is biased against a shoulder provided at the armature of the magnet. The bar 13 supports at its lower end a cutter 17 which cooperates in a known manner with a stationary counter cutter 19 secured to the stitch plate 18 of the sewing machine.

In the embodiment illustrated the counter cutter I9 is seated in a recess provided behind the stitch forming location of the sewing machine. In this manner it becomes possible to arrange the movable cutter l7 and also its counter cutter I9 directly behind the stitch forming location, i.e., below the clamping eyelet of the presser foot 8.

For operating the cutting device a photo electric light gate is provided with a source of light disposed above the material supporting arm which cooperates with a reflector 22 provided in the stitch plate between the needle bar and the cutter operating rod or bar. If the reflector is freed by a work blank leaving the stitch forming location, a ray of light 23 actuates photoelectric cell 21 and in turn the circuit of the electromagnet and any amplifier that might-have been connected in the circuit is briefly closed and the cutter is operated which severs the thread chain closely behind the work blank.

Having described my invention, what I desire to protect by Letters Patent is set forth in the appended claim.

lclaim:

l. Arrangement for severing the thread chain between successive work blanks on a sewing machine having a machine head and a machine arm disposed below said head for supporting material, a needle bar supported in said head and supporting at least one needle, a presser bar disposed behind said needle bar, a cutter rod extending parallel to said presser bar, a cutter supported by said rod and a stationary counter cutter disposed in said machine arm below said cutter rod for cooperation therewith, said presser bar having a circular cross section and said cutter rod being arranged coaxially with said presser bar. 

